My research interests focus on cellular and structural studies of variants of immunoglobulin production in mouse myeloma cells. We have isolated a number of variants synthesizing altered heavy chains after the treatment of the MPC 11 IgG2b producing cell line with the acridine mustard, ICR-191. Altered heavy chains include those which are shorter than the parent, having molecular weights of 50,000 or 40,000 compared to the parental size of 55,000, and those having the gamma 2a serotype of molecular weights 75,000 or 55,000. Primary variants synthesizing chains of 50,000 or 75,000 have been found to give rise to secondary variants synthesizing chains of 55,000 (gamma 2a) or 40,000 (for the 50,000 primary variant) and 55,000 (gamma 2a) (for the 75,000 variant). Our structural studies center on these variant pairs as compared to the parent MPC 11 protein. BIBLIOGRAPHIC REFERENCES: Saija Koskimies and Barbara Birshtein. Primary and Secondary Variants of Immunoglobulin Heavy Chain Production in Mouse Myeloma Cells. Nature 264:480-482 (1976). Tova Francus and Barbara K. Birshtein. Characterization of the IgG2a Immunoglobulin Synthesized by a Secondary Variant of the IgG2b Producing Cell Line of the Mouse Myeloma Tumor, MPC 11. Fed. Proc. 36, p. 1309 (1977). Abs. #5508.